The objective of a climate control system is to provide a comfortable environment to a vehicle occupant, whilst being relatively unobtrusive and avoiding sudden and/or severe changes which may distract the vehicle occupant, along with providing efficient usage of the climate control system equipment.
It will be appreciated that increasingly more sophisticated climate control systems are being incorporated within vehicles, in order to provide comfort and convenience for their users. It is necessary, however, to appropriately direct airflows from such a climate control system in order to maximise performance. It may, for example, prove desirable to defrost/demist window surfaces within the vehicle prior to heating/cooling of the cabin and, in such circumstances, it would be necessary to direct the air flows towards those surfaces.
Major changes between air flow directions may appear to be relatively unpleasant to a user, particularly if the air flow is heated or cooled, e.g. foot level to face level changes.
A sophisticated climate control system could, as depicted in FIG. 1, continuously calculate a control quotient Z in order to set a distribution F of a flap means between a foot level, a bi-level and a face level in order to direct the flow most appropriately.
As can be appreciated from FIG. 1, however, use of a substantially linear relationship for the control quotient Z means you need sophisticated feedback arrangements to provide substantially absolute positional control of flap drive mechanisms, e.g. using servo motors, in order to provide satisfactory bi-level control.
It will be appreciated that calculation of such a control quotient Z for absolute positional determination often includes consideration of a range of environmental factors, such as internal temperature, external temperature, desired temperature, solar load and air flow speed. Thus, a relatively complicated relationship may have to be used in order to continuously derive the control quotient Z and thus adjust, through servo motor control across substantially the whole range, an absolute bi-level position for air flow direction and orientation F. Such sophistication within the climate control system can be expensive and cumbersome.
It will also be appreciated that, typically, environmental conditions within vehicles will not change very rapidly. Thus, the calculation of the control quotient Z will precipitate relatively marginal differentials between actual successive determinations of the value of Z. In previous systems, such as the one as described above with regard to FIG. 1, these marginal changes in the control quotient Z precipitate a reciprocally marginal change in the bi-level position, determined through accurate servo motor control of the air direction flap. Thus, the motor and direction flap are repeatedly altered for only marginal differences in performance.
One example of a quite sophisticated climate control system is disclosed in U.S. Pat. No. 5,156,204 and it is used to provide an appropriate temperature distribution between ventilation used for users and that used for defrosting.
Instead of the absolute determination of a bi-level position F on a linear slope between face level and foot level, a cheaper system might use exclusive orientations and a possible such arrangement is depicted in FIG. 2. In this manner, the climate control system still has a face level, a foot level and a bi-level position but uses a less cumbersome control relationship to derive its control quotient Z. In this case, the control quotient Z is approximated to the nearest exclusive orientation, i.e. foot, face or bi-level.
Although complicated methods of controlling the setting of the flaps are no longer necessary, there is a price to pay in terms of user comfort/convenience. With such cheaper systems there is a noticeable transition between respective foot level, bi-level and face level orientations. This can be particularly uncomfortable for a user when the airflow from the vents is significantly cooler or hotter than the air presently around him. For example, in a simpler system of the type shown in FIG. 2, upon determination of a value for the control quotient Z, a relatively minor change in value may lead to a massive step between the foot level and bilevel, followed by the bi-level to face level and vice-versa.